The compression penalty is actually massive. The bytes you're trying to read might require reading other bytes elsewhere on the disk in order to decompress them

The compression penalty is actually massive. The bytes you're trying to read might require reading other bytes elsewhere on the disk in order to decompress them. It's not just compute power, I was generalising with that statement. The real world speed hit can be as bad as read speeds an order of magnitude slower than if you disable compression. You really only want to compress data where it makes sense to compress it.